this sounds like a bad burn and/or a faulty iso.
how did you download it?
did you check the MD5? (normally not needed if you use bittorrent)
did you burn it at a nice SLOW speed?

many similar problems come from burning too fast, 1-4X is best imho, but do it as sow as you can.
why slow burn? well serch this forum and you will see that a working burn may be "marginal"if to be used as bootmedia.